Stationary vibration isolation systems such as employed in particular for supporting lithography or metrology devices for the processing of semiconductors usually consist of a table which is mounted on a plurality of isolators.
Known from practice are in particular active vibration isolation systems which comprise an active control system counteracting seismic vibrations or vibrations caused by the load (machines) to be isolated. For example, sensors arranged on the floor and/or on the load to be isolated may be used to measure vibrations. The acquired measurement values are used by a control device to actively generate compensation signals which are used to drive actuators for active vibration isolation. In practice, mostly magnetic actuators which are arranged in or on a pneumatic or mechanical (e.g. coil spring) isolator are used to produce counterforces.
With the size of the semiconductor devices to be processed, the size of the systems employed for this purpose also increases. Therefore, the reaction forces that need to be exerted by the actuators are higher and higher, which makes the use of electrically driven actuators more difficult. As a result, a plurality of actuators operating according to the magnetic principle have to be connected in parallel in one direction of action. This is complicated or even impossible in some applications due to the limited installation space available. The use of magnetic actuators is moreover limited by the always existing heat dissipation therefrom.
The need to drive magnetic actuators may certainly be reduced by incorporating a pneumatic level control of the vibration isolation system into the active vibration isolation. However, this is not always sufficient to eliminate the aforementioned drawbacks.
A mechanical vibration isolator comprising a coil spring is disclosed in published patent application EP 2 759 736 A2 (Integrated Dynamics Engineering GmbH).
Published patent application EP 2 998 611 A2 (Integrated Dynamics Engineering GmbH) discloses an isolator comprising an air spring with a characteristic that can be adapted through a replaceable leaf spring assembly and which comprises a bending pendulum to provide an isolating effect in horizontal direction.
However, pneumatic actuators known from practice, such as for example bellows cylinders, pneumatic muscles, and pneumatic cylinders are usually only effective in one direction and are not very suitable for the isolator of a generic stationary vibration isolation system, because of frictional forces existing between the cylinder and the piston, and/or because of force components existing transversely to the actual direction of action.